NCAA rule on same discipline sport competition?

My son heard today that he would not be able to, per an NCAA rule, swim for a school’s NCAA team and also compete as a member of the same schools collegiate triathlon club. Told that triathlon, swimming, track, and XC were consider “same discipline” sports. Wonder why the NCAA would care about this since I thought club teams were not under their jurisdiction. I get why some coaches might care about their athletes training and competing in multiple sports, but not the NCAA. Anyone have any insight on why this is the case?

The athlete could violate the training hours limits or other NCAA rules of accepting support through the other team. Even though the NCAA doesn’t regulate the clubs, the schools often support them through the athletic dept, subsidize them, provide coaches and transportation, provide uniforms, food, facilities.

Would this mean NO club participation by any NCAA athlete regardless of discipline? Was given the impression that he could join cycling club as it is not considered the same disciple as swimming.